1. Field of the Invention
The present invention relates to a method for detecting an electrical fault in an automotive system. More particularly, the present invention relates to a method of detecting an electrical fault in an automotive system, the method accounting for voltage transients which may occur in the system.
2. Disclosure Information
Many systems within an automotive vehicle function between two or more operating states. An example of one such system is a suspension system having multistable suspension units. Suspension units defined as "multistable" can be operated in a plurality of predetermined states. Such suspension units provide control of vehicle ride and handling which may be tailored to particular road surfaces and/or driver characteristics. In typical fashion, a particular state chosen for the suspension unit is determined by a control algorithm with inputs from a variety of vehicle parameters. For example, it is known to control a multistable suspension unit by utilizing vehicle linear acceleration, braking, steering activity, and vehicle speed as well as through a manually operable mode switch. U.S. Pat. No. 4,621,833, assigned to the assignee of the present invention, discloses a system for operating multistable suspension units, including feedback of the operating mode of each suspension unit. Other systems within the vehicle, such as climate control, braking, engine, and various body electronics also function between two or more operating states and are suitable for use with the method of the present invention in detecting a fault within such system.
Typically in these types of systems, an actuator such as a motor, a solenoid, relays and the like associated with a switching device place the system into a desired operating state. If the actuator fails to place the system into the desired state, the system may generate an error message and simply shut down until serviced. The error messages may be generated even though there is no actual fault within the system, the error message being generated because of an electrical transient, such as a voltage transient present within the system. Various methods and systems have been proposed for detecting faults within automotive systems, such as are shown in U.S. Pat. Nos. 4,082,218; 4,780,826 and 4,550,286. However, none of these patents teach or suggest any system which discounts a fault signal when the vehicle power supply is outside of predetermined limits, thus negating the fault signal due to electrical or voltage transients.
Other systems have been proposed for detecting power supply voltage transients or conditions that can disable the controlling central processing unit (CPU) such as are shown in U.S. Pat. Nos. 4,016,408; 4,307,389; 4,399,538; 4,461,003; 4,503,479; 4,673,912; and 4,903,208. In these patents, the CPU is disabled when an abnormal voltage transient is detected even though the sensors and controlling systems may have been functioning properly before the voltage transient was detected. The patents do not teach that during the time interval when the actual voltage transient began and when it is detected, the control system may have already been operating erratically and that the input sensing methods may have been providing faulty data signals. Therefore, it would be desirable to have a system wherein the input data recorded prior to the detected voltage transient or undesirable voltage condition would be ignored or treated as inaccurate prior to the generated fault signal.
These and other advantages of the present invention will become apparent from the following summary, detailed description in claims which follow.